Process of recovering acetic values from a. cellulose-acetate mixture



May 5, 1925.

1,536,312 P. c. SEEL PROCESS OF RECOVERING ACETIC VALUES FROM A CELLULOSE ACETATE MIXTURE Filed April 2. 1924 Relaiibel caarie arzffrles of a celluialse acemfe m xfare co iaz zg rolazlle acefme are 41 as U611 as cefzc ac'd razed 137v info fz r wer paTfl c/es 4 aseazqs Vefizde sued as e ai' aii; 7.? passed info calliaaz? Z WIM iize fire/Te pm izdes to fake 14 up mfiditj afacetu: Values I x l Vehicle is relied/e The aseaus V9 tale is moved along as 83 a.

compressor a Mower Ace/lb valued, suck as aceh'c acid are W/waredfrom fie gafieous febitle, as 53 coolzny and condswamg Paw GSeel,

Patented May 5, 1925.

PAUL o. SEEL, or ROCHESTER, nEwYonx,

ASSIGNOB TO EASTMAN KODAK COMPANY,

OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS OF RECOVERING- AGETIC VALUES FROM A CELLULOSE-ACETATE MIX TUBE.

Application filed April 2,

1 tion.

This invention'relates, to processes for re-' covering acetic values from cellulose acetate lnixturesj One object of the invention is to provide a process for recovering such values from sucha mixture when the latter is already in the form of powderygrains, such as the intermediate product orv powder produced in my prior Patent No. 1,494,816, granted May 20, 1924, for process of mama facturing cellulose acetate. Another object of the invention is to provide a rapid and inexpensive process for breaking. up such powder and volatilizing acetic values therer from. Other objects will hereinafter ap pear.

In the accompanying drawing, the single figure is a diagrammatic side elevation, partly in vertical section, showing one form of apparatus in which my process may be carried out,.the relative sizes of the parts beingexaggerated for the sake of clearness. When a cellulose acetate reaction mixture containing initially cellulose, acetic anhy dride, acetic acid and sulfuric acid, or some other well known condensing agent, is allowed to react and the excess of acetic values are evaporated, especially with agitation of the mass, tl1ere is produced a powder, the grains'of which do not coalesce upon standvery large surface relative to its mass. Be-- A cause of this, it may be rapidly treated with liquids and such treatment, moreover, will be uniform with respect to all the particles, thus insuring substantial homogeneity as'a result of the treatment.

\Vhen the powdery mass is produced from the cellulose acetate reaction mixture, in

' vehicle mg at .room temperature and pressure.-

1924. Serial N0. 703,738.

which the cellulose acetate is in solution so long as the particles of the powder remain substantially separate. Because,.however, of the difficulty of removing the last residual portions of acetic values from the powder by continued blowingin the apparatus described in my hereinabove 'cited application, it becomes advisable for economical reasons to carry the evaporation only down to the point where the acetic values form less than half of the weight of the powder. A powder in which 30% of the weight consists of acetic values is a typically useful one.

For some purposes it is desirable to free 'the cellulos'e acetate, even from these small residual acetic values. Moreover, it is-degreat surface relativeto the mass 1s mainta1ned,1n other words,

.sirable at the same time to recover such;

values economically. I have found that this can be done by breaking up the grains of powder into relatively finer particles, thereby exposing the interior portions of the particles, and permitting the acetic values to vaporize through .the new surfaces thus formed. Preferably these vapors are taken up by a fluid vehicle and carried away, the

values being finally extracted from the like.

,This method of treating the granular or powdery mass may be carried out in many.

by absorption, condensation, or the tration, but it will be understood that the invention is not restricted thereto.

Referring to the accompanying drawing,

1 represents the apparatus in which the grains or relatively coarser particles, of

are divided and broken open, so as to expose the interior portions thereof. This is preferably done by any of the well known which the initial powdery mass ismade up, Y

mechanical devices capable of grinding, rub- .bing or breaking the particles of the mass.

While edge runners, mortars and pestles, and the like could be employed, I prefer to use a pulverizer of the high speed rotary to a large "number ofimpacts repeated with great frequency. The repeated blows, to

' blade type, in which the charge is subjected] the pipe 6 to the removal station "T, which may be any one of the known absorbing or condensing units employed for this purpose. The gas, freed from a considerable portion of the vaporsof acetic values, next passes throughpipe 8, being moved by any suitable form of blower or impeller 9 driven, for example, through any suitable means, here illustrated as pulley 10 and belt 11, coacting with pulley 12 of motor 3. The gas is preferably warmed by any suitable heating unit 13 before it passes through pipe 14 to apparatus 1. It will thus be seen that the gas passes through the same cycle repeatedly, thereby avoiding loss into the atmosphere of residual vapors of acetic values not removed at station 7, if the gaswere discharged after leaving station 7 instead of being recirculated. If station 7 takes the form of a condenser, it is convenient to keep it at a temperature around 60" F., for example, too low a temperature tending to solidify the acetic acid and choke the system. The temperature in apparatus 1. however, is conveniently kept at 80 to 85 F., and

" heating unit 13 may be used to bring the cooled air back to such proper temperature. Of course, .the temperatures mentioned above are merely illustrative and subject to adjustment, as will be understood by those skilled in the art. Vhere rapidly moving beating blades are used in apparatus 1,.a thorough intermixture of the gaseous vehicle and the broken particles is readily ob I tained. Any suitable dust-trapping apparatus may be used to prevent the fine particles from passing out into pi e 6.

Having thus described my invention, what I claim as new and desire to secure by LettcrsP-atent is: a Y

1. In'tlie process of making cellulose ace- .tate which includes recovering acetic values ffrom a cellulose acetaten ixture which is in the form of relatively coarse part cles containinginsufficient of said values to cause cellulose acetate mixture in the form of rela tively coarse particles containing acetic values in quantities insuilicient to cause said particles to coalesce at room temperature and pressure, the ste s of mechanically breaking open said particles to form a powder of relatively finer particles, thereby ex posing interior portions of said first named particles, and passing a gaseous vehicle through said broken particles to carry away vapors of acetic values therefrom.

3. In the process of recovering acetic acid from a cellulose acetate mixture which is in the form of relatively coarse particles having on their outer surfaces insuflicient acetic acid to cause them to coalesce at room temperature and pressure, the steps of mechanically breaking up said particles to form a powder of relatively finer particles, "thereby exposing interior surfaces of said first named particles, passing air into contact with said broken up particles to take up and .carry away acetic acid vapors and separating acetic acid from said air. a

4. In the process of manufacturing cellulose acetate'the steps of further pulverizing by violent impacts a powder comprising substantially separate particles of a mixture of cellulose acetate and acetic acid, passing air through the pulverized particles to take up acetic acid, and separating acetic acid from said air.

5. In the process of manufacturing cellulose acetate which includes the preparation of a cellulose acetate mixture in the form of relatively coarse particles containing acetic values in quantities insufficient to cause said particles to coalesce at room temperature and pressure, the steps of breaking up said particles into finer particles and repeatedly circulating a gaseous vehicle through said broken particles to take vapors of acetic values, and through a removal zone for removingiacetic values from the vehicle.

Signed at Rochester, New York, this 26th day of March, 1924.

. i PAUL C. SEEL. 

